The present invention concerns an internal combustion engine comprising a plurality of cylinders and at least one turbocharger and at least one exhaust manifold which passes exhaust gases from two or more cylinders to the turbocharger.
Arrangements of that kind are known in accordance with the state of the art. The term exhaust manifold is used generally to denote the conduit communication between the cylinder head outlet and the turbocharger intake in the case of multi-cylinder engines. Those exhaust manifolds are usually either in the form of an uncooled and heat-insulated conduit assembly or they are of a water-cooled structure. In the case of a water-cooled arrangement the exhaust gas-carrying pipes are surrounded by a cooling water jacket, as is shown for example in DE 810 554 C, DE 42 07 048 C1 and DE 42 06 249 C1. Exhaust conduits of that kind are used inter alia in marine and explosion-protection sectors where high surface temperatures have to be avoided. In situations involving stoichiometric engine operation, water-cooled exhaust conduits are also used by virtue of the extremely high gas temperatures as otherwise the severe development of heat results in overloading of the materials carrying the exhaust gases. Alternatively in the case of a marine engine with a plurality of exhaust conduits it is also known from DE 27 21 614 A1 to provide a water-cooled intermediate plate between the exhaust gas conduits and the turbocharger for thermal decoupling purposes.
When the entire exhaust gas manifold involves a great cooling effect in terms of area the engine cooling water is greatly heated whereby thermal damage can be caused to the engine. With cooling involving a small area the exhaust gas is not sufficiently cooled down so that critical turbine intake temperatures can result in overheating of the turbocharger.